A method of simplifying the selection of a color profile for the conversion of color coordinates from one color space to another, where there are a number of color management attributes, each having a number of values, by assigning a value of “wildcard” as one possible value to one or more attributes, thus making it possible to use one profile for a number of values of that attribute.
In the typical document generation process, a user at a terminal creates a document in page description language. One element of the document may be a color picture in some industry standard set of colors such as red, green and blue (RGB), and may also contain a list of one or more attributes such as paper type or halftone screen arrangement. These are sent to a particular printer for printing, and there, must be transformed into the color space that the target printer uses, such as cyan, magenta, yellow, black (CMYK). In addition, the resultant set of CMYK colors must be adjusted to fit the attributes of the particular printer, such as the media reflection type and glossiness of the paper and the color characteristics of the printer toner. All of these color processes are typically combined into a single table look-up which accommodates the color space conversion, and the attributes mandated by the user and printer.
More specifically, for each input pixel, the three input colors, such as RGB, are used to address a three dimensional (16 by 16 by 16, for a numerical example) cube of values (a profile), and interpolation is used for fractional distances between node values, to generate a three-color, CMYK, output pixel.
The problem is that for even a moderately complex printer, the number of combinations of attributes, and therefore, the number of profiles, becomes too large. For example, in a system which can print on four kinds of paper, can use paper with four different types of glossiness, using four different halftone patterns, and one of four types of lighting, 256 profiles would have to be stored.
Further, if an attribute value is called for and no profile exists for that value, the printer may not print. An alternative would be for the printer to select an available profile which may result in a poor quality image.
An improved method is needed for reducing the number of profiles required, or in the alternative, guaranteeing that a reasonable image will be printed in any case.